Officers were called just before 4am to a report of a woman said to be in possession of a substance.
London Ambulance Service says two members of staff “were exposed to the substance” and they remain under investigation.
Firefighters “conducted a sweep of the premises” and removed a chemical from the scene.
Met Police statement.
Police were called at 03:46hrs by London Ambulance Service to reports of a woman having ingested poison at an address in Thornton Heath.
The woman was taken to a south London hospital by LAS where she was found to be in possession of a possible hazardous substance.
Officers and London Fire Brigade attended Croydon University Hospital and safety cordons and closures were established while specialist officers examined the item and safety procedures were enacted.
Ambulances and emergency vehicles were given access to the hospital throughout the incident response.
Road closures have since been lifted.
There were no arrests.
